1. Field of the Invention
The present invention relates to a positive photosensitive composition used in a manufacturing process of semiconductor, such as IC, manufacture of circuit substrates for liquid crystals, thermal heads and the like, and other photo-fabrication processes, and a pattern-forming method using the same. More specifically, the invention relates to a positive photosensitive composition suitable for use in cases where an exposure source of far ultraviolet rays of wavelengths of 220 nm or shorter and an irradiation source of electron beams are used, and a pattern-forming method using the same.
2. Background Art
Chemical amplification photosensitive compositions are pattern-forming materials capable of generating an acid at an exposed area irradiated with radiation such as far ultraviolet rays, changing the solubility in a developing solution between the irradiated area with the actinic radiation and the non-irradiated area by reaction with the acid as a catalyst, and forming a pattern on a substrate.
In a case where a KrF excimer laser is used as an exposure light source, since resins having poly(hydroxystyrene) small in absorption in the region of 248 nm as a fundamental skeleton are mainly used, a good pattern having high sensitivity and high resolution can be formed as compared with the conventional naphthoquinonediazide/novolak resins.
On the other hand, when a light source of a shorter wavelength, e.g., an ArF excimer laser (193 nm), is used as an exposure light source, even the chemical amplification series resists are not sufficient, since compounds containing an aromatic group substantially show large absorption in the region of 193 nm.
Therefore, resists containing a resin having an alicyclic hydrocarbon structure have been developed for an ArF excimer laser.
Further, it has been found that by the introduction of a repeating unit having a lactone structure into the resins having an alicyclic hydrocarbon structure, the performances of the resins are improved. There are disclosed in patent literature 1 (JP-A-9-73173 (the term “JP-A” as used herein refers to an “unexamined published Japanese patent application”) and patent literature 2 (U.S. Pat. No. 6,388,101B) resist compositions using resins containing repeating units having a mevalonic lactone structure and a γ-lactone structure, and in patent literature 3 (U.S. Patent 2004-63,882A), patent literature 4 (U.S. Pat. No. 6,746,818B), and patent literature 5 (U.S. Pat. No. 6,720,430B), resist compositions using resins containing a repeating unit having an alicyclic lactone structure are disclosed.
As for acid generators that are the main constituents of chemical amplification resist compositions, also, various kinds of compounds have been found and compounds capable of decomposing and generating a sulfonic acid upon irradiation with actinic rays are generally used. Further, as compounds that generate acids other than a sulfonic acid, photosensitive compositions containing a sulfonium salt or an iodonium salt having a bissulfonyl imide anion or a trissulfonyl methide anion are disclosed in patent literature 6 (JP-A-2002-268223), patent literature 7 (JP-A-2003-261529), and patent literature 8 (U.S. patent 2003-148,221A).
However, from the viewpoint of synthetic performances as resists, it is really very difficult to find combinations of resins, light-acid generators, additives and solvents to be used, and further, in forming a pattern having a line width as fine as of 100 nm or less, a line pattern formed collapses even if resolution performance is excellent. Accordingly, the improvements of the problem of pattern collapse that causes defects in manufacture of devices and the performance of line edge roughness of a line pattern have been required.
Here, line edge roughness means that the edge of the interface between the line pattern of a resist and a substrate presents an irregular form distorted perpendicularly to the line direction, attributing to the characteristics of the resist. When this pattern is observed from right above, the edge looks unevenly (± several nm to several ten nm or so). Since this unevenness is transferred to a substrate by etching processing, electric characteristic failure is caused if the unevenness is great, which results in the reduction of yield.